Three variations of the AR-15 assault rifle used to kill 49 people in an Orlando nightclub (AP)

The massacre of 49 people at an Orlando nightclub has raised questions about access to guns in the US - assault rifles, in particular.

In Florida, buying one is no problem so long as you are 18, a legal resident of the United States, have not been convicted of a serious crime, are not a domestic abuser and have no documented mental health or substance abuse issues.

:: All firearm purchases from federally licensed dealers require a background check, regardless of whether the buyer has a concealed weapons permit.

:: There is no waiting period to buy a rifle. There is a three-day waiting period to buy a handgun, and handgun buyers must be 21 or older.

:: People charged with or convicted of a felony (a more serious crime) cannot buy guns. Neither can people who have two or more drink-driving convictions, have been involuntarily committed to a mental health hospital or have a restraining order against them.

Brian Malte, the national policy director for the Brady Campaign to prevent gun violence, said getting a gun is far too easy in Florida - and added that private firearm sales do not require any background checks at all.

"The corporate gun lobby seems to use Florida as their example, and unfortunately we've seen what that example has produced, including George Zimmerman, who had a history of violence and an arrest record and yet was able to carry a concealed gun," Mr Malte said, referring to the neighbourhood watch volunteer who fatally shot unarmed black teenager Trayvon Martin in 2012.

"Florida is certainly no shining example of gun laws."

Former Florida Department of Law Enforcement Commissioner Gerald Bailey believes the state gets it right on firearms. He ran the agency which conducts background checks for gun purchases.

"I've had an opportunity to look at what a lot of states are doing. Florida is ahead of the pack with what they're doing with firearms," Mr Bailey said. "It works as well in Florida as it does anywhere else."

Of course, some of the disqualifying issues, like mental health and substance abuse, would have to be self-reported if there is no record of the problem.

Mr Bailey said people cannot be denied a gun just because other people think they're mentally ill.

"Not in a free society," he said.

"There has to be some sort of determination that that person is mentally incompetent."

Florida also requires training and a background check before someone can get a licence to carry a gun in public - but very few people are denied.

There are about 1.6 million concealed weapons permit holders in the state. In the past 19 years, only 24,713 applications have been denied, and 17,557 of those were because the application was not filled out properly, and not necessarily because the applicant did not qualify.

Former agriculture commissioner Charlie Bronson, who ran the agency which issues the permits, does not believe gun laws need to be changed.

He said assault rifles like the AR-15 Omar Mateen used in the Orlando attacks are also used for legitimate purposes.

"People use AR-15s to hunt deer, to hunt hogs, to hunt all kinds of game," he said.

"Think of the over one million people that have them and have never misused them, and they want to do away with certain aspects of the gun permitting or buying weapons because of one person's lawlessness."

Mateen bought his gun legally at the St Lucie Shooting Centre.

Gun store owner Ed Henson said Mateen passed a full background check, and that if he had not bought the guns from him, he would have purchased them somewhere else.

Mr Henson told reporters outside his business that he is sorry an "evil person" bought the guns from his shop.